Short answer
A fake IW323721 is a replica of an IWC Ingenieur Automatic from the IW3237 group. The trailing 21 is a variant code for one dial and strap combination. Replica sellers ask $250 to $600. Genuine IW3237 watches trade on the used market in a range that starts near $3,500 and can pass $7,000 for a full set with box and papers. The price gap is why the copies exist. The finish gap is how you catch them.
What the reference covers
IWC reference codes pair a base number with a variant suffix. IW3237 is the base. IW323721 means IW3237 with variant 21. The caseback engraving carries both parts, so read it first.
The Ingenieur is IWC's antimagnetic sports line. Steel case, screw-down crown on most variants, and a soft-iron inner case on several references in the line. Bracelet links meet the case with a close fit, which is a hard thing to copy at low cost.
Two items I could not confirm from public sources: the caliber number fitted to IW323721 and its exact case diameter. Ask IWC service for both, or check the numbers on a genuine example before you compare.
What replicas copy and what they skip
Replica factories copy what shows in a phone photo. They skip what needs a loupe, a scale or a bench.
- Case: measure the diameter with calipers. A copy that is 0.3 mm off spec will not take a genuine strap or bracelet end link.
- Bracelet: check the gap at the lug line in a side photo. Look at the clasp engraving depth.
- Dial: check the print on the IWC logo and the Ingenieur name. Copy print sits heavier and fills the counter of the letters.
- Date: compare the numeral shape in the window with an IWC press photo.
- Crystal: genuine watches carry anti-reflective coating on both faces. Many copies coat the outside face alone.
- Weight: ask for grams. A steel case and bracelet weigh more than a plated brass case.
Checks to run before you pay
- Request a photo of the caseback engraving with the reference and serial in focus.
- Request a movement photo with the rotor text readable. A genuine IWC rotor carries the brand mark and a caliber number.
- Send the serial to IWC service and ask for a record check.
- Request a video of the seconds hand and the date change.
- Request the weight in grams and the case diameter in mm.
- Ask for the warranty card and the service booklet. A full set adds value on resale.
Price points
Replica: $250 to $600 for a copy of an Ingenieur Automatic. Above $600 you pay for a cloned movement and cloned rotor decoration, not for better steel.
Genuine used: check live listings on the day you buy. IW3237 prices move with condition, service history and whether the box and papers are present. A watch with no service record needs a $500 to $900 service budget on top of the price.
Customs and legal risk
A watch that carries an IWC mark and is not an IWC watch is a counterfeit under US and EU import rules. Customs officers can seize the parcel and destroy it. The seller carries the paperwork risk at the border, not the buyer, but the buyer loses the money paid. A replica sold as a replica is a different case from a counterfeit sold as genuine, and the second one is fraud.